Description

Abstract:

The image is a sun shaded representation of a grid generated from seismic interpretation of the depth to the top of the subsurface glacial sediments of the Merrimelia Formation and fluvial outwash sands of the Tirrawarra Sandstone in the Cooper Basin area in the north-east of South Australia. This grid is part of a database of seismically mapped subsurface time and depth, grids, contours, faults and polygons interpreted from Seismic mapping over the Cooper Basin area.

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Data Quality

Lineage:

Source data are hydrocarbon exploration seismic geophysical surveys, and well velocities and lithologies.

The depth structure map was made by creating from well values, the isopach from the top Tirrawarra Sandstone / Merrimelia Formation to top Basement grid, then adding this to the Basement depth grid, to give the correct subsea depth.

Isopach intervals from wells were gridded and contoured. Constraints were created in the form of isopach contours to remove anomalous or incorrect grid gradients. In addition, constraints were added to ensure conformity with logical stratigraphy, such as thickening on the down throw side of major faults and thins on major anticlinal structures.

The isopach was regridded and contoured using both well values and constraining contours. Resulting grid/contours were checked for accuracy and conformity, to structural and stratigraphic principles, and edited again. Areas devoid of these units were directly masked out using polygon boundaries. This iterative process was repeated until a satisfactory map was achieved. The resulting isopach grid was then added to the Basement grid, checked and edited until a final depth grid was achieved.

Positional Accuracy:

Pixel size

Attribute Accuracy:

The accuracy at wells that penetrate the Tirrawarra SS or Merrimelia Fm is within 2 metres of the well top Tirrawarra/Merrimelia picks as interpreted pre June 1999. Between wells the horizon is constrained between the Basement grid and the Patchawarra Formation grid.